Lasers are often used for image projection because they can provide narrow emission bandwidths and high brightness. However, laser light also tends to have a high degree of coherence which can cause speckle in images projected using the laser light. Such speckle can appear as artifacts visible to viewers, thereby degrading the quality of the projected image.
To mitigate speckle, some projector designs use moving components in the optical path of the laser beam to reduce the coherence of the beam and therefore reduce speckle. However, such moving components tend to be prone to mechanical wear and failure. In addition, many of these components tend to increase the etendue of the laser beam that can be used to project the image.